Method of securing counter current contact of fluids by centrifugal action



June 19361 w. J. PODBIELNIAK 4,9.

METHOD OF SECURING COUNTER CURRENT CONTACT OF FLUIDS BY CENTRIFUGAL ACTION Original Filed Aug. 18, 1930 2 Sheets-Sheet l June 1936- 'w. J. PODBIELNIAK 2,4,99 METHOD OF SECURING COUNTER CURREN'I CONTAGT OF FLUIDS BY CENTRIFUGAL ACTION Original Filed Aug. 18, 1930 2 Sheets-Sheet 2 Patented June 23, 1936 UNITED STATES PATENT OFFICE METHOD or sscuamc ooun'rl-za coaasn'r oomacr or rwms av cns'rmr- UGAL ACTION Walter J. Podbielniak, Chicago, Ill., assignor to Lois W. G. Podbielniak, Tulsa, Okla.

Original application August 18, 1930, serial No.

Divided and this application May 1,

1935, Serial No. 19,327. In Qanada August 12,

19 can. (Cl. 261-83) and-may be utilized for purposes of distillation and fractionation, absorption, or contacting of partly or wholly immiscible liquids, although not limited to such processes. In order that the invention may be fully understood, it is exemplified herein in connection with a-process for the fractional distillation of fluids having constituents of different boiling points. The invention is not limited to such processes, nor the details thereof as set forth herein. This application is divided from my prior application Serial No. 476,190 flied August In order that the objects and accomplishments of the invention may be most fully and clearly understood in connection with the securing of effective counter current contact between fluids, I

shall discuss preliminarily some of the problems and difliculties commonly met with in attempting to accomplish precise or close fractionation, a process in which such contact is required to a high degree; and I shall also mention briefly the V short-comings of the usual type of fractionating apparatus which render such apparatus incapable of effecting close fractionation in the distillation of fluids or mixtures having the characteristics hereinafter mentioned. In the commercial or laboratory distillation of liquid mixtures having constituents or fractions of various boiling points, it is frequently desirable, and in many cases essential, to be able to fractionate the mixture with such closeness as to isolate the constituents in substantially their pure state. For example, in

the distillation of crude petroleum or other mixtures of similar complexity of composition, it is desirable for numerous reasons to be able to fractionate the crude into constituents ranging in 0 volatility from the lightest to the heaviest, with such closeness or sharpness of separation that the fractions or cuts will consist of the constituents of the mixture in substantially pure conditions, or of compounds which together have a very close boiling range. An extremely difficult problem in counter current contact is thereby presented.

In certain of the more eflicient types of common fractionating apparatus, fairly close fractionation of the more volatile constituents of a mixture may 50 be brought about. For instance, the highly volatile constituents of natural gas ranging say from methane through the pentane fractions, may be isolated in a'fairly pure state by the use of hig y efllcient and properly designed fractionating columns, particularly in small scale laboratory equipbetween the liquid and gaseous phases.

ment. However, when it is attempted to separate the fractions or constituents of comparatively higher boiling point and higher molecular weight, whether in troleum or other complex mixtures, heretofore" surmountable diiflculties have beenencountered such as prevent precise fractionation and isolation of the higher boiling point constit- 'uents,.due chiefly to the increasing complexity of isomeric compounds for any given boiling range, and because of the extreme closeness in boiling point of many of these heavier constituents. In

, order to approximate close fractionation of such mixtures by the usual types of fractions-ting apparatus, extremely high or long fractionating columns are required. However, even these fail to 15 accomplish the separation of the heavier fractionswith the desired closeness when such fractions reach the higher boiling. ranges and complexity of molecular structure. Insofar as I am aware, the separation of the heavier fractions having boiling points within a range of about 6 C., cannot be accomplished by fractionating equipment heretofore employed, whether" in laboratory or commercial scale distillation. It may be stated that from an analytical standpoint, it isdesirable to determine the exact composition of petroleums and other similar complex mixtures, and to be able to carry the analysis of the mixture through the heaviest constituents which it maycontain.

By the method of the present invention, I am enabled to secure a fractional distillation by which volatile mixtures may be separated into their pure constituents, or single compounds, or into fractions having an extremely close boiling point range which may be as low as 1 C. or less. The invention provides further a method of securing the effectiveness of counter current contact necessary to accomplishing such close fractionation without the requirement for large and'complicated equipment. A

In order to secure the contact conditions necessary to attain precise fractionation of the heavier and more complex fractions of petroleum crudes, for example, by ordinary methods, there would be required a fractionating column of unreasonably and impractically great length or height. The reason for this will be readily understood by those familiar with the art, ,since the commonly accepted theory of fractional distillation involves the idea that the degree of closeness t with which any two fractions may be separated depends upon the intimacy and time of contact An ideal column which would accomplish perfect separation between the constituents of a mixture would #11 though the theoretical requirement of itesi= malliquid or vapor holdup is of primary importanee in batch distillation, in any case minimum liquid and vapor holdup is a practical ad vantage in decreasing the size of the equipment and amount of desirable constituent held up.

Aside from practical considerations of dimculty, inconvenience, and expense involved in constructing fractionating columns of length substantially greater than those now in use, such construction is made impossible due to the fact that in the usual fractionating column, gravity is relied upon to cause the liquid or reflux to flow downward and counter-currently to the assending vapor within the column. Hence, the usual fractionating column must, of course, be built vertical and designed and given such dimensions that the vapor will not hold up the liquid flow or cause the liquid to be entrained or carried by the vapor stream. It necessarily follows then that the vapor velocity must be held within certain comparatively low limits by building the columnswith correspondingly large diameters, in order that the vapor velocity will not become so high that the reflux liquid is carried with the vapors, thereby resulting' in priming or flooding of the column. I may also state that suflicient clearance or spacing between the plates of the column must be allowed in order to avoid priming, and in many cases the factor of clearance alone may necessitate building a fractionating column of very great length.

Because heretofore gravity has been resorted to as a means for bringing about counter current flow and contact of the reflux liquid with the vapor, a limit has been reached as to the emciency which such apparatus may have, in that although the advantages of building columnsoif much greater lengths has been well appreciated, the impracticability from engineering and economical standpoints has prevented such construtions. Accordingly the emciency oi the appsratus has been limited by the practical consider= ations involved.

The present invention departs from the usual methods for securing counter current contact, as in fractional distillatiomin the utilization and adapting of a different force in bringing about counter-current flow and contact of the vapors and the reflux liquid. Instead of causingthe reflux to flow by gravity, 1 bring about countercurrent flow oi the reflux by centriiugal force, taking advantage or the diflerence in specific gravity of the fluids involved, which are the reflux and the vapor. By the aid oi centritugai force, the reflux may be caused to flow at a high rate through a fractionating column or tube of small diameter or clearance,- therehy reducing the amount of liquid and vapor held in (the to:- umn to a mlnimuni, and without interference with the flow of the reflux .by the" vapors, since J by virtue of the differences in specifio gravities' .oi the two fluids, they are caused to follow separate and non-interfering paths. Also the centrifugal force maybe made to overcome very much greater "interferences or pressure drops. which normally WOlfld'OCClLl, than would be possible with-gravity alone. By so employing cen triiugal 'force, the fractionating column or tube may be built or mounted in the form of a rotat able channel or passageway such as a coil,'en-=' abling the entire column to be built in anem- ;,inaftcr, to employ liquid seal joints in which 'liquid such as mercury is used as the sealing metremely compact form, and to be of practically any desired length without involving prohibitive constructions. A clwe approach to the ideal v tion broadly contemplates the use of centrifugal 15 force in efiecting intimate and extended contact of a liquid with a gas or vapor or one fluid with another, in a variety of situations in which the object of the operation is to bring about contact between the relatively lighter and relatively heavier fluids. For example, instead of subjecting a liquid and gas or vapor to this action for the purpose of fractionating the constituents thereof, the present method may be employed for effecting vaporization of fairly volatile constituents of the liquid, or for loading the liquid with or causing to be absorbed therein, certain constituents in or carried by the vapors. This latter procedure will be readily recognized as that followed in absorption systems wherein an absorbing liquid, by virtue of extended and intimate contact with a. vapor or gas, is caused to hold or absorb certain desirable constitutents of the gas which are subsequently recovered by separation from the absorbing liquid. It is obvious also that the centrifugal force will remove from the vapors or other relatively lighter fluid, entrained particles heavier or denser than the fluid from which it is desired to free them by throwing such particles into the liquid.

For purposes of describing the-,invention, I show herein a type of construction which is adapted to-operate in accordance with my improved method.- However, it will be understood that the invention in its broader aspects is in no way to be regarded as limited to the method of operation or the particular construction shown herein since, as]; have stated, the hereinafter described form oi? the invention is but typical of a variety of constructions that may be used 50 in practising the invention.

The apparatus herein disclosed for practising the invention comprises a contacting or fractionating tube in spirally coiled form carried on a rotatable body or support. Vapors are fed to 55 the tube and reflux is returned to the tube through stationary inlet and outlet lines. Fluid tight stufiing boxes or joints are provided between the rotatable contacting tube and the stationary inlet and outlet, and although in the broader aspects of the invention any suitable type of fluid tight connection may be provided be tween the column and the inlet and outlet, I prefer, for reasons that will be made apparent herediam. The connections between the tube and thevapor' supply vsource, and the outlet and refiua'condenser are such as to permit heavier frac tions not vaporized in the'tube to be returned through the inlet to the vapor supply source or V still, and the condensate from the refluxcon= denser to be returned through the outlet to the fractionating tube.

The above mentioned objects and aspects of 75 the invention, as well as the various features of the form in which it is illustrated herein, will be understood from the following detailed description, reference being had throughout the description to the accompanying drawings, in which:

Fig. l is a general view, diagrammatic in parts, illustrating a suitable apparatus for carrying out the invention, the showing of the insulating layer about the contacting tube coil being omitted for purposes of more clearly illustrating the arrangement and mounting of the tube;

Fig. 2 is an enlarged vertically contractedsectional view taken through the fractionating apparatus; and

Fig. 3 is a reduced sectional vie on line 3-4 of Fig. 2.

Referring first to Figs. 1 and 2, numeral II) denotes generally the centrifugal apparatus which comprises a rotatable mounting shell or body ll comprising a vertical shell, which may suitably, though not necessarily, be of conical shape as indicated, and so designed that both liquid and vapor throughout the bulk of the coil length are continually forced along the desired directions through centrifugal force. It will be understood that the supporting means or body may be of various constructions and shapes and that the contacting tube or passageway, hereinafter described, may accordingly be arranged in a variety of manners. The shell II is supported on a circular bottom plate l2 which in turn rests on a hollow and downwardly tapering base I3 of cir-- supporting and Journaling the supporting structure at its upper and lower ends, the bearing arrangement. shown in the drawings being intended as typical only. The described supporting structure may be rotated by any suitable drive means, such as pulley 20 keyed to the lower tubular portion Ila of the base and driven from motor 2| by gears 22,pulleys 23 and belt 24.

Mounted on the supporting structure exteriorly of shell II is a spirally wound contactingtube or column 25, which opens at its lowerend 2512 through the bottom plate l2 into the interior 2B of the base l3, and at its upper end at .25!) through the wall of shell ll into chamber-W1. It will be understood that although for; purposes of illustration I show a contacting or fractionating tube coil having a comparativelysmall; n inher of turns, the apparatus may be builtso 'as vapor inlet to the fractionating apparatus.

and fractionation in the spiral tube or column 3 action in maintaining the fluids or different densities in separate paths of flow and permitting the use of greater velocities, as will more fully appear hereinafter.

Heated vapors to be subjected to rectification wardly through the lower sleeve portion I 3a of the rotatable base I 3 to a point somewhat below plate l2. Pipe 32 may be regarded as a stationary In order to prevent fluid leakagefrom the interior space 28 within base l3 around the inlet pipe 32 to accommodate a coil of very great length and.

consisting of a correspondingly great number of turns. In order to maintain the propertemperature and equilibrium conditions in the tube, the' coil may be thermally insulated with a layer 21,

of suitable thermal insulating material (Fig. '2),

and since during operations the coil may be re-- 'tionating tube and pipe 32 may be ineffective,

. lar plate or vane il which is spaced at 35 a suitable distance from plate 12,. The outer portion 5 of plate 34 projects within an annular liquid seal chamber or recess 36 formed between plate I! and the upper flanged portion [3!) of the base. A

" suitable number of pipes or conduits 38, two being shown as typical, extend from pipe at a 0 suitable distance below its upper end, to openings 89 located in plate 34 a radial distance from the center thereof corresponding to the radial distance of 'the lower open and 25a of the fractionating tube. Assuming the tubular coil to be rotated 5 in the direction indicated by arrow A in Fig. 3, tubes, preferably will be given attheir upper ends a curvature as indicated at a, so that the tubes will extend substantially in line with the diagonally downward path in which the liquid 40 discharged from the lower end of the fractionating tube will tend to follow due to the rotation of the .tube.

Within base l2 and directly below flange 13b is an. annular trough M which, when the appa- 45 ratus is stationary, contains a suitable sealing flow of the mercury into the sealing chamber.

The provision of a mercury seal joint of the character shown between the stationary inlet 60 pipe 32 and the rotating fractionating tube is of particularadvantage inthat the parts of the seal :are entirely free from wear, as distinguished from v the usual type of stuffing box within which acompressed packing is used. Also; due to the 05 great centrifugal force holding the mercury in .theliquid seal chamber, the mercury will not become" displacedto one side of the sealing vane 34 to such an extent as to permit passage of other fluids throughthe sealing liquid, even by extreme- 7o ly high difleigential pressure at opposite'sides ofv the-vane.

The vapors passing'out of the upper-end of a the fractionating tube into the chamber l! are. conducted through a stationary outletline 40,

supported by bracket ill, to the reflux condor 58, wherein the heavier fractions of the vapors may be condensed by a suitable cooling fluid introduced to the condenser through illness and discharged through line to. The uncondensed vapors item the reflux condenser are conducted through line 55 to suitable condensing means, not shown. The reflux condensate irom the condenser 48 is returned through line 52 to the vaoor outlet line Q6, from whence the reflux pwses into chamber ii and into the iractlonating tube.

A mercuryseal, generally indicated at 53 and similar in principle-to the lower seal shove described, is provided between the upper rotating extension is of the suoporting structure and the stationary outletiplpc to. The seal to comprises a hollow housing M consisting of a lower plate 55 joined at so to tubular portion ac, and an/upper plate El having a reduced diameter sleeve portion 58 which may be fitted more closely to pipe so in order to close of! the escape oi any vapors that may be lathe housing at such times as the mercury seal may be broken. Mounted on the outlet pipe is a circular plate or vane so which forms a barrier between opposite sides of the mercury seal in the same manner es the lower plate 3 5. The bottom 55 of housing cs may be.

cupped us at 55a in order to accommodate sufficlent mercury'to effect the seal. Upon rotation of the housing to operating speed, the mercury rises to the oositlon indicated at ti, thereby sealing between the spaces within the housing above and below the vane, and causing vapors from chamber ll to pass into the outlet line.

In the operation of the apparatus, the vapors from still 33 pass upwardly through the stationary pipe 332, the major nortlon oi the vapors flowing through the upper portion 32a of the inlet into space to, although some oi the vapors may be conducted into that space through the conduits til. The vapors then pass into the lower end 25a of the iractioriating tube 25 and upwardly through the tube into cer l! and the outlet line 58 leading to the reflux condenser. M oreviously stated, the reflux is returned through the outlet to chcmber H, from whence it fiows outwardly through the'fractionatiug tube 25 and counter-currently to the ascending vapors, into space 35. Due to its greater specific gravity, the reflux-liquid in space 35 is maintained at the outside of the opening 25c and does not interfere with the how of vapors into the tracticnating tube. Liquid in space 35 passes downwardly -through conduits 38 and line 3''? to the evaporator.

The counter-currently flowing reflux and vs.- pose in the contacting or iractionating tube, due

' to the action or the centrifuge] iorce thereon. will be caused to allow .in separate psths, the reflux, by virtue of its higher snecmc gravity, being caused to flow along the outside interior wall of the tube, and the vapors belng forced to follow a oth at the inside of the reflux. Thus the two fluids are maintaln'edun non-lnterterlng paths o! flow with the result that a'hlgh raterof flow through the tube may be obtained without causing'the prevlously mentioned phenomenon of priming; or in other words, without causing reflux liquid to be ickering: and carried by the vapor stream. And olthough the liquid and vapors follow separate paths, it willbe noted that the two ore maintained in intimate and extended exposure since the or surface of the liquid stream is in direct con t with the vapors, so, that the centrifugal force presses the lighter fluid against the heavier one to increase their intimacy of contact, the heavier fluid being in turn pressed against the wall of the tube by the centrliugal force. A further advantegeous result is brought about by the centrifugal action in that there is a tendency tor the heavier constituents of the vapors to be thrown to the outward section of the vapor stream in contact with the reflux, so that the heaviest constituents of the vapors will be maintained in the most intimate contact with the reflux. the effectiveness of which in bringing about the greatest iractionating efilclency will be readily apparent to-those familiar with the theories of fractionation-by rectification. Any solid or liquid particles initially entrained with the vapor or other-relatively lighter fluid likewise will he forced; irom the lighter into contact with the relatively heavier liquid by centrifugal action. Also the lightest of the liquid components will tend tobe brought to the llquidwapor interface, to obvious advantage. The most advantageous speed of rotation of the column may vary, but I may state that satisfactory results have been attallied revolving the column at a rate of about coco a. r. or.

Since the reflux and vapors are maintained in 'mon-interterlng paths of flow, it follows that the passageway or fractionating tube may be of practlcally any length desired, since increasing the length of the tube will in no way act to retard the free counter-current passage of the liquid and vapor. And for similar reasons, it will be apparrent that the tube or passageway may be of greatly reduced diameter or clearance, even though the velocities of the liquid and vapors cussing therethrough are high, since no interference will 35 occur which will occasion priming as the result of high velocity. I

By proper control of the reflux, the composition of the vapors passing through the outlet line M to suitable final condensers may be controlled 40 so that the condensate will consist, if desired, of one constituent of the mixture being evaporated, in substantially its pure state; or the condensate my consist of an extremely close-cut fraction, the boiling range of which may be as low as within 1 C. or less. The heavier liquid constituents returned from the tractionatlng tube to the still may be revaporized and the various fractions or constituents subsequently obtained as final conden sate in the order of their decreasing volatility, as separation of the mixture constituents proceeds. The emciency of the apparatus is such that dise tillatlon curves plotted to represent the range through which distillation is carried will indicute, in the case of separation of constituents co While I have described and illustrated on apparatus particularly adapted to perform the method of my invention as applied to fgactionatlngyapors derlvedirom distilling complex liquids such as crude petroleum, it will be understood that I do not limit myself to such particular field of application o l-the process or method of my invention, which may be utilized to modify the constituents of a fluid by counter-current contact with another fluid oi! different density, such fluids being at least immiscible, and one or both of which may be a liquid, as in absorption processes, and other counter-current treatment processes.

I-claim:

1. The method of modifying fluids comprising flowing fluids of different densities counter-currently in direct contact through a passageway of increasing radius while maintaining continuous communication between the source of said condenser fluid and the inlet to saidpassageway, rotating said passageway to develop centrifugal force and utilizing such forceto force said denser fluid outwardly through the pasageway in contact with the outer wall thereof. v

2. The method of modifying fluids comprising flowing fluids of different densities counter-currently in direct contact through a passageway of increasing radius, rotating said passageway to de velop centrifugal force and cause the heavier fluid 'to move outwardly through the passageway, and

forcing the lighter fluid to move inwardly through the passageway in contact with the heavier fluid.

3. The method of securing intimate contact between a liquid and a fluid of lower density which comprises supplying the liquid within a conveying channel shaped in a curve ofprogressively increasing radius, rotating said channel to develop centrifugal force sufilcient to, cause the liquid to travel outwardly through the channel and forcing the lower density fluid to pass through the channel in the reverse direction.

4. The method of securing intimate contact between a liquid and gas which comprises supplying the liquid within a conveying channel shaped in a curve of progressively increasing radius, rotating said channel to develop centrifugal force sufficient to cause the liquid to travel outwardly through the channel and forcing the gas to pass through the conduit in the reverse direction.

5. The method of separating the constituents of a gas or vapor mixture by fractional condensation which comprises forcing the mixture in-- wardly through a conveying channel formed in a curve of progressively increasing diameter, supplying cooling liquid in said channeL'androtating the channel to develop centrifugal force therein whereby cooling liquid and condensate formed therein are forced to travel outwardly through the channel counter-currently to the gasiformf mixture.

6. The method of separating the constituents of a vaporizable liquid which comprises heating the liquid to form a vapor mixture, forcing the Va por mixture inwardly through a conveying channel formed in a curve of progressively increasing diameter, supplying cooling liquid in said conduit. and rotating the channel to develop centrifugal force therein whereby cooling liquid and conden- 4 sate formed therein are forced to travel outwardly through the channel counter-currently to the gasiform mixture and discharging uncdndensed va por from the inner end of the conduit. '7. The method of fractionally separating the constituents of a gas or vapor mixture that includes causing said mixture to fiow inwardlythrough a spiral conveying channel, supplying a cooling medium within the channel, and simultaneously rotating the channel to force condensate to fiow therethrough counter-currentlyto @the vapor mixture.

8. The method of separating the constituents of a vaporizable liquid which comprises heating conveying channel, supplying a cooling medium within the conveying channel and simultaneously of a. gasiform mixture by fractional condensarotating the conveying'channel to force condensate to flow therethrough counter-currently to the vapor mixture and discharging uncondensed vapor from the inner end of the conduit.

9. A method of conveying materials during 5 treatment which comprises continuously feeding the material to a spiral conveying surface, continuously distributing the material along said spiral conveying surface by rotating said surface in such a manner as to distribute and maintain the material thereover in a film, and subjecting said. distributed material, while being so conveyed, to direct contact with a treating gaseous or vaporous medium moving in a direction opposite that of the treated material, taking substantially all of the resultant vapors off'atone end of the spiral and the residueof the treated material at the other end thereof.

10. In a method of treating materials capable of distribution over a surface by flow with a vapor or gaseous treating medium, said method including conveying said material during the treatment while maintaining continuous communication between the source of said material and the inlet to said surface and distributing and 2 maintaining it in a film along a spiral path, progressively changing the properties of said material by infinitesimal steps from the initial stage of the treatment to those of the flnal stage of the treatment by subjecting said conveyed and distributed materials to a gas or vaporous treating medium, and causing substantially all gases and vapors to traverse said path in acounter direction to the movement of the material therein.

11. A method of treating materials including distributing and maintaining the material in a film during treatment along a closed spiral conveying channel while maintaining continuous communication between the supply of said ma- Y terial and the inlet of said channel by rotating 40 and final stages of treatment and in counter direction to that of said treated material. 12. The method of bringing about intimate contact between a liquid and-vapor or gas that comprises supplying the liquid to the inner end of a spiral conveying channel, rotating the spiral channel to develop such centrifugal force as to cause said liquid to travel outwardly through .said channel and supplying the vapor or gas to the outer end of said channel and forcing it to pass therethrough counter-currently to the liquid.

13. The method of separating the constituents tion which comprises moving a cooling liquid by centrifugal force outwardly'in a confined path of progressively increasing radius; and forcing the mixture inwardly in said path in contact with 'said cooling liquid to cause condensates from said mixture to be carried outwardly by said cooling liquid counter-currently to said gasiform mixture.

14; A method for effecting a counter-current 7 movement between fluids having different specific grav'ities which comprises passing the heavier density fluid outwardly through an elongated uninterrupted confined passageway of increasing radius, passing the other fluid in a reand rototing said new to deveiop oentriiugal iorce sumoient to ermit. said fluids to flow in reverse directions in substantially continuous 15. A method for efiectinga counter current movement between fluids of difierent densities which comprises passing the denser fluid outwardly through an elongated uninterrupted passageway of increasing radius having a restricted cross-sational area, passing the other fluid in,

reverse direction through said passageway and rotating said passageway to developcentrliugel force sumcient to permit said fluids to flowdn reverse directions in suhstantiaily continuous streams.

1B. A method for effecting a .counter current movement between a liquid and a fluid of lower density comprising flowing the liquid outwardly through an elongated uninterrupted passageway of increasing radius. forcing the fluid of lower density in a reverse direction through said gosssageway and rotating said eway to develop centrifugal force suihcient to maintain the n in. n -11ke 10m- 17. me method or modifying fluids comprissesame liquidand fluid of lower density in continuous ing flowing fluids o! difierent, densitiescontinuously oountertly in direct contact through a confined warn oi incre radius, rototing said eway to develop centriiugal ior'ce and us such iorce'tofiow one of said fluids on 1 through the passageway in contact with the outer wall thereof.

18, The method of senaratingthe constituents of a gasii'onn mixture by fractional condensa- 19. The methodot modifying fluids oi diiier- 20 out dmsities which consists in causing the fluid of greater density to move outwardly in an advancing spiral path and the fluid oi lesser density "to move inwardly in a contracting spiral path in contact with and in a oounterflow to the fluid 25 of greater density.

--WALIER J. POD

In". i 1

CERTIFICATE OF CORRECTION. 7

Patent No. 2,044,996.. June 23, 1936,

WALTER J. PODBIELNIAK.

It is hereby certified that error appears in the printed specification oi the above numbered patent requiring correction as follows: Page .3, first column, line 8-9, claim 1, for the word "condenser" read denser; line 12, same claim, for "pasageway" read passageway; and second column, lines 38 to 40 inclusive, claim 11, strike out the words"while maintaining eontinuous communication between the supply of said material and the inlet of said channel" and insert the same after "channel and before the coma in line 41, same claim, and that the said Letters Patent should be read with these corrections therein that the same may conform to the record 01 the case in the Patent Office. Signed and sealed this 22nd day of September, A.- D. 1,936.

Henry Van Arac li,

(Seal) Acting Commissioner of ?atents. 

